Question

When r is equal to n, there is only one combination. why is this true?​

Answer 1

Let's say both n = 3 and r = 3.

An example problem could be something like "We have 3 people to pick from and 3 seats to fill".

Each person would get their own seat. The order doesn't matter in a combination, which is why there's only one combination possible. A group like A,B,C is the same as B,C,A.

So in this case,
`_3C_3 = 1` and more generally
`_n C_n = 1` for any positive integer n.